This week's book giveaway is in the Reactive Progamming forum. We're giving away four copies of Reactive Streams in Java: Concurrency with RxJava, Reactor, and Akka Streams and have Adam Davis on-line! See this thread for details.
Solr can index PDFs and subsequently search them; it can not convert PDFs to any other format (nor can it do that for any other format - that's just not what Solr does). But PDFs in general are not amenable to format conversion.